Taphole for a metallurgical vessel



Sept. 6, 1967 K. w. HANSEN 3,343,827

TAPHOLE FOR A METALLURGICAL VESSEL Filed April 29, 1965 Fig.2

//VV/V70A. KENNETH w. HANSEN United States Patent 3,343,827 TAPHOLE FORA METALLURGICAL VESSEL Kenneth W. Hansen, Bethe] Park, Pa., assignor toHarbison-Walker Refractories Company, Pittsburgh, Pa., a corporation ofPennsylvania Filed Apr. 29, 1965, Ser. No. 451,803 6 Claims. (Cl.266-33) ABSTRACT OF THE DISCLOSURE Taphole for a metallurgical vessel ofceramically bonded inverted U-shaped conduit segments in interlockingrelationship nested in a surrounding layer of monolithic refractorymaterial.

In the processing of molten steel, in furnaces such as the basic openhearth and the basic oxygen furnaces, refractories having a high degreeof erosion resistance must be employed in the metal contact area. Onesuch area of these vessels, which is vulnerable to erosion is thetaphole of the vessel. The taphole of a metallurgical furnace may bedisposed in various locations depending on furnace type. For example, inthe basic open hearth, the taphole is located below the molten metalbath, while in the basic oxygen furnace, it is located above the metalbath and the furnace is tilted to allow gravity flow of the molten metalthrough the taphole.

In the formation of basic open hearth tapholes, by prior practice, asteel pipe, generally ranging from 2 to 6 in length was placed in thetaphole area and an unconsolidated refractory mix was rammed or castaround the pipe to hold it in place. After the first tapping of afurnace heat, the steel pipe would melt out and a completely refractorytaphole would result. However, these tapholes are physicallyunsatisfactory for various reasons. The ramming and casting mixes had tobe, of course, placed in the furnace in an unburned state and thus couldnot attain the maximum density and strength necessary to developsuflicient erosion resistance necessary to satisfactorily survive afurnace heat. Further, the density and strength of the tapholes werenonuniform from end to end.

It has been suggested to prefabricate a combination of castable andmetal pipe. There has also been some sug-' gestion to employprefabricated refractory sleeves to form the tapholes. However,physically satisfactory refractory sleeves have not been fabricatedeconomically with known forming apparatus, particularly long onesranging up to 6 in length.

Another problem confronting prior workers, particularly in basic openhearth furnace operation, is the dissipation of molten metal and slagwhich has accumulated on the furnace bottom below the taphole inrefractory areas that have eroded or worn away. Before the recharging ofthe furnace for another heat, the molten metal and slag must be removed,preferably through the taphole, so that the furnace bottom can bepatched, where necessary, or relined. The general practice for removingthe molten metal is to burn a passage with an oxygen lance along thelower perimeter of the taphole between the taphole opening and thefurnace hearth to the depth of the accumulated molten metal so that themetal will flow through the taphole. The formation of a suitable passagewas not too difiicult with completely rammed or cast tapholes because oftheir susceptibility to erosion. However, tapholes containing preformed,burned refractory sleeves presented a dilemma. The sleeves were designedto withstand erosion and thus were very difiicult to provide with apassage. Therefore, it was desirable to fabricate a taphole having thesuperior refractory properties of preformed, burned refractory sleeves,yet being amenable to enlargement in depth at the lower perimeterthereof to facilitate removal of accumulated molten metal below thetaphole in the hearth.

Accordingly, it is an object of the present invention to provide ataphole for a metallurgical vessel composed of a preformed, prefiredrefractory sleeve and one that is readily amenable to enlargement at thelower perimeter thereof to facilitate removal of accumulations of moltenmetal below the taphole opening.

Another object of the present invention, is to provide a means forfabricating a taphole for a metallurgical vessel consisting ofpreformed, prefired refractory shapes.

Still another object of the invention is to provide tapholes for basicsteelmaking furnaces that may be readily replaced between furnace heats.

Other objects of the invention, will in part, appear hereinafter.

In order to more fully understand the nature and scope of the invention,reference should be had to the following description and drawings inwhich:

FIG. 1 is a perspective view of a taphole conduit segment employed infabricating a taphole according to the present invention; and

FIG. 2 is an elevation view, partly in cross section, illustrating thetaphole area of a basic open hearth furnace.

Briefly, in accordance with one embodiment of the present invention,there is provided a metallurgical vessel having a molten metalcontaining chamber and a taphole. The taphole is lined with a composite,longitudinally joined refractory conduit nested in a surrounding layerof monolithic refractory material. The conduit is composed of aplurality of prefabricated, ceramically bonded, inverted U-shapedcylindrical conduit segments. Each segment includes a passage for moltenmetal between the end surfaces thereof. Further, the end surfaces ofeach segment are provided with complementary interlocking means, suchas, tongues and grooves, for mating with an adjacent segment. Theconduit segments are arranged in series and are complementarily mated toprovide an integral taphole conduit having a continuous molten metalpassage.

The taphole conduit segments may be fabricated by methods well known inthe refractories art. One method includes forming a stiff mud-likemixture of selected refractory material, vibration casting and thenburning at a suitable temperature to impart maximum strength. However,the most economical and preferred method of fabrication is by mixing theselected refractory material with a tempering agent and ramming themixture in a mold conforming to the contours of the conduit segments toobtain good densities in subsequent burning. In either method, theburning and ceramic bonding may be carried out after the segments areassembled into an integral unit, if the burning kiln can accommodate thecomplete unit. An advantage of firing the segments before assembly isthat the segments may be shipped to the job site where they areassembled without great risk of damage.

The conduit segments may be composed of any basic refractory materialscharacterized by relatively good erosion resistance in contact withmolten steels produced in the basic open hearth and basic oxygenfurnaces. The preferred refractory materials for use in the furnacesmentioned are dead burned magnesite and dolomite and mixtures thereof.Other basic refractory materials hav- Patented Sept. 26, 1967 ingrelatively good erosion resistance would also be satisfactory. Theserefractories may be tar bonded or tar impregnated and contain variousother refractory ingredients known in the art to impart superiorphysical properties. A particularly useful refractory sleeve is composedof an extremely refractory dead burned magnesi-te material of highpurity periclase having a magnesia content of at least about 90% byweight.

Referring to the drawings, in FIGURE 1, there is shown a taphole conduitsegment 20 having a U-shaped cross section. The conduit segment containsa molten metal passage 22. At one end of the segment is located an innerperipheral projection or tongue 24 and at the other end is located aninner peripheral depression or groove 26.

Referring to FIGURE 2, there is shown a typical taphole area of a basicopen hearth furnace 39. The furnace contains an outer metal shell 32 anda refractory lining therein. In the taphole area, the lining consists ofa supporting layer or lining of burned basic brick 34 with a sufficientarea left open for the taphole. An inverted U- shaped taphole conduitcomposed of prefabricated and fired conduit segments 40 is then insertedin the taphole area and is held in place with a ramming or casting mix42. The conduit is formed by mating together the complementary tonguesand grooves of a series of segments and securing them into a unit.

Generally, a refractory cement is not necessary at the tongue and groovejoints, since at the operating temperatures of the vessel the conduitsegments will expand slightly to provide a sufficient seal. However,refractory cement may be employed, if desired, as an added safety factoror to facilitate installation.

After the monolithic lining is built up in the taphole area to asufficient height, the inverted U-shaped conduit is disposed on thelining immediately, before drying, so that the leading edges of theinverted U-shaped conduit will impale the monolith to provide arelatively tight molten metal seal therewith.

The monolithic refractory material is then rammed or cast around theconduit, filling all the voids between the conduit and brickwork. It ispreferred that a suflicient volume of the monolithic refractory 42 beemployed around the taphole conduit, so that when the conduit must bereplaced, it can be readily scraped or burned out or the like and a newconduit inserted and secured in place in a similar manner. A tapholespout 44 may then be secured to the outer shell 32.

With the taphole construction of the invention, only the lower perimeterof the taphole, between the leading edges of the inverted U-shapedconduit will be subject to appreciable erosion. However, the erodedareas may be readily patched between furnace heats. This tendency toerode is exceeded in importance by the facility of providing a passagetherein to allow the accumulated molten metal below the taphole to flowfrom the furnace.

The length and radius of the taphole conduits will vary according to thesize of the furnace and the thickness of the supporting and workinglinings maintained therein. However, generally, for a basic open hearthfurnace they are about in length and have an inner radius of about 3".Each of the prefabricated segments would measure about 12" to 14" inlength.

As was pointed out previously, the completely rammed or cast tapholeshad relatively nonuniform density and strength. Contrariwise, theprefabricated, ceramically bonded conduit of the present invention ischaracterized by substantially uniform and relatively high density andstrength at substantially all points of contact with the molten metaland have proved to be satisfactory in service.

In addition to the other advantages discussed above for the presentinvention, it should be noted that our use of many separate burned unitsto form the taphole discharge advantageously serves to lessen theeffects of thermal shock which might be expected if a single unit hadbeen used. The many joints between the composite units serve to breakthe continuity of heat travel from one end of the tube to the other,thereby preventing disastrously steep thermal gradients from occurring.Yet further, should the thermal gradient in any given section be such asto cause cracking, stresses would-in some parttend to concentrate in thejoints between sequential units. Cracking in this area would not allowescape of molten metal for two reasons. First, the tortuous flow path,because of the nesting cooperation between adjacent tubes, together withthe inherent relatively high viscosity and surface tension of the moltenmetal, will tend to depress any runout of metal.

In has been noted elsewhere that castable tends to shrink in service,and fire shaped of the type herein discussed tend to expand. True, thedegree of expansion and shrinkage is quite minor. However, if too rigida composite structure exists, cracking, spalling, or like destructivephenomena could occur. In the present construction, the shrinkage of thecastable and expansion of the preformed, burned, conduit sectionstogether cooperate to dampen or at least compensate to some extent theirrespective shrinkage and expansion.

It is intended that the foregoing description and drawings be construedas illustrative and not limiting.

Having thus described the invention in detail and with suflicientparticularity as to enable those skilled in the art to practice it, whatis desired to have rotected by Letters Patent is set forth in thefollowing claims.

I claim:

1. The combination with a metallurgical vessel having a molten metalcontaining chamber and a taphole, said taphole being lined with acomposite, longitudinally joined refractory conduit nested in asurrounding layer of monolithic refractory material, composed of aplurality of prefabricated, ceramically bonded, inverted U-shapedcouduit segments having opposite ends provided with interlocking meansfor mating with an adjacent segment in molten metal sealed relation,said conduit segments being complementarily mated to provide acontinuous molten metal passage.

2. The vessel of claim 1, in which the conduit segments are composed ofat least one material selected from the group consisting of dead burnedmagnesite and dead burned dolomite.

3. The vessel of claim 1, in which the conduit segments are composed ofan extremely refractory dead burned magnesite material of high puritypericlase having a magnesia content of at least by Weight.

4. The vessel of claim 1, in which the complementary interlocking meansof the conduit segments consist of tongues and grooves.

5. The combination with a basic open hearth furnace having a moltenmetal containing chamber and a taphole, said taphole being lined with acomposite, longitudinally joined refractory conduit nested in asurrounding layer of monolithic refractory, said monolithic refractoryforming a portion of the taphole lining in a longitudinal direction atthe lower perimeter thereof, said conduit being composed of a pluralityof prefabricated, ceramically bonded, conduit segments, each segmentincluding a passage for molten metal between end surfaces thereof, theend surfaces of each segment being provided with interlocking means formating with an adjacent segment in molten metal sealed relation, saidconduit segments being complementarily mated to provide a continuousmolten metal passage.

6. The combination with a basic open hearth furnace having a moltenmetal containing chamber and a taphole, said taphole being lined with acomposite, longitudinally joined refractory conduit nested in asurrounding layer of monolithic refractory, said conduit being composedof a plurality of prefabricated, ceramically bonded, conduit segments,each segment including a passage for molten metal between end surfacesthereof, the end surfaces of each segment being provided withinterlocking means for mating with an adjacent segment in molten metalsealed relation, said conduit segments being complementarily mated toprovide a continuous molten metal passage, said taphole being amenableto enlargement in the longitudinal direction only at the lower perimeterthereof, without deleteriously affecting said taphole conduit, so as toprovide a means of egress References Cited UNITED STATES PATENTS1,184,634 5/1916 Duerrwachter 26346 X 1,565,084 12/1925 Frerichs 266-422,839,825 6/1958 Edwards et a1 264-30 X 2,845,261 7/1958 Furczyk 266-33J. SPENCER OVERHOLSER, Primary Examiner.

for molten metal present in the furnace below the taphole. 10 E. MAR,Assistant Examiner.

1. THE COMBINATION WITH A METALLURGICAL VESSEL HAVING A MOLTEN METALCONTAINING CHAMBER AND A TAPHOLE, SAID TAPHOLE BEING LINED WITH ACOMPOSITE, LONGITUDINALLY JOINED REFRACTORY CONDUIT NESTED IN ASURROUNDING LAYER OF MONOLITHIC REFRACTORY MATERIAL, COMPOSED OF APLURALITY OF PREFABRICATED, CERAMICALLY BONDED, INVERTED U-SHAPEDCONDUIT SEGMENTS HAVING OPPOSITE ENDS PROVIDED WITH INTERLOCKING MEANSFOR MATING WITH AN ADJACENT SEGMENT IN MOLTEN METAL SEALED RELATION,SAID CONDUIT SEGMENTS BEING COMPLEMENTARILY MATED TO PROVIDE ACONTINUOUS MOLTEN METAL PASSAGE.